Optical modules containing an optical semiconductor device have been used for optical communications. If a high frequency signal having a transmission rate of 10 Gbps or higher is applied to these optical modules, reflections will occur due to an impedance mismatch between the stem and the optical semiconductor device, resulting in degraded transmission characteristics. To solve this problem and thereby improve the transmission characteristics, conventional optical modules additionally include a resistive element for impedance matching which is disposed near the optical semiconductor device (see, e.g., Japanese Laid-Open Patent Publication Nos. 2006-128545, 2003-37329, and 2003-332667).
However, such a conventional optical module configuration is disadvantageous in that the added resistive element prevents the optical module from operating at increased temperature and with reduced power consumption.